Search results for "CERAMICS"
showing 10 items of 1599 documents
Multinucleated giant cells in the implant bed of bone substitutes are foreign body giant cells-New insights into the material-mediated healing process
2017
In addition to macrophages, multinucleated giant cells (MNGCs) are involved in the tissue reaction to a variety of biomaterials. Especially in the case of bone substitute materials it has been assumed that the MNGCs are osteoclasts, based on the chemical and physical similarity of many materials to the calcified matrix and the bony environment in which they are used. However, many studies indicate that these cells belong to the cell line of the foreign body giant cells (FBGCs), which are of "inflammatory origin", although they have been shown to possess both a pro- and also anti-inflammatory phenotype. Moreover, no information is available about their role in the tissue reaction to bone sub…
Synthesis, characterization and thermal properties of new aromatic quaternary ammonium bromides
2004
Series of new aromatic R 2R′ 2N +Br - (R=benzyl, 4-methylbenzyl, 2-phenylethyl, 3-phenylpropyl; R′=ethyl, methyl, isopropyl) or RR′ 2NH +Br --type (R=benzyl, R′=isopropyl) quaternary ammonium bromides were prepared by using novel synthetic route in which a formamide (N,N-diethylformamide, N,N-dimethylformamide, N,N-diisopropylformamide) is treated with aralkyl halide in presence of a weak base. The compounds were characterized by 1H-NMR and 13C-NMR spectroscopy and mass spectrometry. Structures of the crystalline compounds were determined by X-ray single crystal diffraction, and in addition the powder diffraction method was used to study the structural similarities between the single crysta…
A New Conducting Molecular Solid Based on the Magnetic [Ni(dmf)6]2+ Cation and on [Ni(dsit)2]22− (dsit=1,3-dithiole-2-thione-4,5-diselenolate) Showin…
2002
The synthesis, X-ray structure, magnetic and transport properties of the compound Ni(dmf) 6 [Ni(dsit) 2 ] 2 (dmf=dimethylformamide, dsit = 1,3-dithiole-2-thione-4,5-diselenolate) are described. This compound crystallizes in the monoclinic space group P2 1 /c, with a = 18.709(6), b = 22.975(5), c = 20.418(5) A, β = 99.31(2)° and Z = 6; its structure consists of [Ni(dsit) 2 ] 2- 2 dimers and isolated [Ni(dmf) 6 ] 2+ cations both centrosymmetric and non-centrosymmetric. The dimers are packed forming chains along the [101] direction with short Se...Se interdimer contacts. Additional interchains S...S contacts render this structure a three-dimensional character, never observed so far in other [N…
Synthesis of β- and γ-carbolines via ruthenium and rhodium catalysed [2+2+2] cycloadditions of yne-ynamides with methylcyanoformate
2011
A flexible approach towards substituted β- and γ-carbolines based on transition metal catalysed [2+2+2] cycloaddition reactions between functionalised yne-ynamides and methylcyanoformate is described. The versatility of this new reaction sequence is demonstrated by its application in the total synthesis of the marine natural product eudistomin U.
Mechanical properties of basalt fiber reinforced composites manufactured with different vacuum assisted impregnation techniques
2016
Abstract This work describes an experimental mechanical characterisation campaign on composites made out of a quasi-unidirectional basalt fabric. In order to evaluate the ability of commercial basalt fabrics and their composites to meet the potentials of basalt fibers, the work has used raw materials from commercial catalogs with no further modification. Two common manufacturing techniques for medium performance composites have been adopted: vacuum assisted resin infusion, and hand-impregnated vacuum bagging. Two panels, one for each technique, have been fabricated, able to provide a sufficient number of samples for a comprehensive stiffness and strength characterization through Tensile, Fl…
A technical note on an experimental device to measure friction coefficient in sheet metal forming
2006
Abstract In the paper the authors present the results of several experimental tests aimed to determine the Coulomb friction coefficient in sheet metal forming operations at the varying of the sheet metal material and for different operative conditions. In particular a few pressure and lubricating conditions have been investigated. In order to develop such experiments a dedicated fixture was designed and set-up starting from the one proposed by Wilson.
Radiation induced generation of non-bridging oxygen hole center in silica: Intrinsic and extrinsic processes
2007
Abstract The generation of non-bridging oxygen hole center ( Si–O ) was investigated in a wide variety of natural (fused quartz) and synthetic silica samples exposed to different γ- and β-irradiation doses by looking at its optical bands. We distinguish two different generation processes: intrinsic associated with the cleavage of Si–O bond and characterized by a sublinear law and extrinsic due to the conversion of OH precursor characterized by a growth curve with a saturating tendency. The interplay between the two processes and the role of H are discussed.
Growth of paramagnetic defects by gamma rays irradiation in oxygen-deficient silica
2005
Abstract We report an electron paramagnetic resonance (EPR) study of gamma rays irradiation effects on an oxygen-deficient silica obtained from fused quartz. We have found that three types of E′ centers, E α ′ , E γ ′ and E δ ′ , and a paramagnetic defect in a spin triplet state (S = 1) are induced. The EPR signals dependence on the microwave power have been investigated. The concentrations of these centers as a function of gamma ray irradiation show that for high dose a limit value is reached suggesting a generation process from precursors.
Luminescence of GeO2 glass, rutile-like and α-quartz-like crystals
2006
Abstract The luminescence of GeO 2 rutile-like crystals was studied. Crystals were grown from a melt of germanium dioxide and sodium bicarbonate mixture. Luminescence of the crystal was compared with that of sodium germanate glasses produced in reduced and oxidized conditions. A luminescence band at 2.3 eV was observed under N 2 laser (337 nm). At higher excitation photon energies and X-ray excitation an additional band at 3 eV appears in luminescence. The band at 2.3 eV possesses intra-center decay time constant about 100 μs at 290 K and about 200 μs at low temperature. Analogous luminescence was obtained in reduced sodium germanate glasses. No luminescence was observed in oxidized glasses…
Effect of pressure and temperature on viscosity of a borosilicate glass
2018
International audience; During industrial glass production processes, the actual distribution of stress components in the glass during scribing remains, to date, poorly quantified, and thus continues to be challenging to model numerically. In this work, we experimentally quantified the effect of pressure and temperature on the viscosity of SCHOTT N-BK7 glass, by performing in situ deformation experiments at temperatures between 550 and 595 °C and confining pressures between 100 MPa and 300 MPa. Experiments were performed at constant displacement rates to produce almost constant strain rates between 9.70 × 10 −6 s-1 and 4.98 × 10-5 s-1. The resulting net axial stresses range from 81 MPa to 8…